A Radar Climatology of Tropical Anvil

The vertical structure of reflectivity observed by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) and CloudSat Cloud Profiling Radar (CPR) is used to investigate the geographical distribution and temporal variability of tropical anvil (i.e., thick, non-precipitating cloud associated with deep convection). Based on 10 years of TRMM measurements from 1998 to 2007, anvil observable by the PR occurs 0.2% of the time across the tropics and has an average echo top about 7.7 km and an average thickness about 2 km. In order to quantify the amount of anvil that the PR is missing, coincident PR-CPR overpasses were examined. Statistics show that the TRMM PR underestimates anvil top height by 1 to 10 km with an average of around 5 km. A similar calculation concerning areal coverage is underway. Anvil occurs more often and is higher and thicker over land than over the ocean. Some tropical land regions, especially those affected by monsoon circulations, experience significant annual variability in anvil properties. Strong interannual anvil variability occurs over the central Pacific due to ENSO. Geographical and temporal anvil variations can be related to precipitation characteristics, as well as features of the large-scale environment (e.g., shear, humidity, and aerosols). For example, the anvil to rain area ratio is highest over the Atlantic ITCZ, an area that is affected by Saharan dust transport. The ability to observe and model the occurrence and vertical extent of anvil is essential in capturing the energy and water budget of the tropics.